Originally Posted by zj97ltd
If, when you cleaned your IAC, you twisted or pushed on the little plunger, you may have ruined it. Or you may just have a loose vacuum line.
Every time I clean my IAC I push the plunger back in a bit. When I reinstall it my idle speed will jump to 1500 - 2500 rpm but after ten seconds or so it will start to drop in roughly 200 rpm increments as the computer adjusts. Take a minute to get back to normal but I know my IAC works.
Last time I unscrewed it all the way and gave the innards a good squirt of white lithium grease.